Challenges arose from body effect in design of implant and on-body antennas, has dominated bodyarea network base station antenna design researches. However, design of an efficient base station antenna in a compact size is also a challenge. This letter presents a miniaturized omni-directional antenna in two bands of 403.5 MHz for medical implant communication services (MICS) and 2.45 GHz for industrial, scientific and medical (ISM) applications.

The antenna consists of two stacked center-fed circular patch over a circular ground plane. The upper and lower patches resonates in MICS and ISM bands, respectively. Each patch is loaded with two vias for miniaturization. The achieved miniaturization factors are 6.3 and 5.1 for MICS and ISM bands, respectively. Since the TM010 mode is excited, the pattern is omnidirectional with a null in broadside. The measurement results show a good agreement with the simulation in terms of reflection coefficient and radiation pattern